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A negative value of J integral before cracking
Posted May 16, 2023, 6:40 p.m. EDT 1 Reply
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Hi all, I wonder if you have ever got a negative value when computing the J integral? In structure mechanics module, I add a thermal strain which can evolve with time. In this case, the J integral is a negative number. It seems that the thermal strain affected the computational process. Any solution to this problem?
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The derivation of the standard path independent J-integral makes use of the fact that the stress tensor is divergence-free. This rules out (most) body loads, as well as thermal strains.
A correction term (a surface integral) is needed. You can find an expression for this term (Eq. 26) in https://www.researchgate.net/publication/200092866_Numerical_Aspects_of_the_Path-Dependence_of_the_J-Integration_in_Incremental_Plasticity .
-------------------Henrik Sönnerlind
COMSOL